Electric-furnace wall construction



May 29, 1923.. 1,456,893

7 G. M. LITTLE ELECTRIC FURNACE WALL CONSTRUCTION Filed May 24, 1.921

WITNESSES; INVENTOR Wm .v

ATTORNEY Patented May 29, 1923.

UNITED STATES PATENT OFFICE.

GEORGE E. LITTLE, OI PITTSBURGH, PENNSYLVANIA, ASSIGNOB TO WESTINGHOUSEELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

ELECTRIC-FURNACE WALL CONSTRUCTION.

Application filed lay 24, 1921. Serial No. 472,095.

To all whom it may concern:

Be it known that I, Gnonon M. Lima, a citizen of the United States, anda resident of Pittsburgh in the county of Allegheny 5 and State oflennsylvania, have invented a new and useful Improvement in Electrlc-Furnace Wall Construction, of which the following is a specification.

My invention relates to electric furnaces l and particularly toelectric-resistance furnaces and it has for its object to provide meansfor "reducing leakage current between the current-conducting electrodes.

In my co-pending application, Serial No.

1 454,776, filed March 23, 1921, I have disclosed an electric-resistancefurnace in which the heating element comprises two substantiallyparallel members, each of which is provided with an elongated electrodeextendin through the furnace wall.

I have foun that, under certain conditions of operation of a furnace, ofthe character designated, there is a relatively large leakage of currentbetween the two elec- 2 trodes, especially if the bricks of the wallengage the electrodes and especially so if the temperature of thefurnace is raised to a relatively high value.

In practicing my invention, I build up a portion of the furnace wallimmediately adjacent to, and surrounding a part of the electrodes with aplurality of thin plates of refractory high-temperature-resistingmaterial which plates may be separated either by a layer of granularmaterial between successive plates or by a plurality of integralprojections on the plates themselves. The resistance to the passage ofan electric current between successive plates is thus increased manytimes by the use of either the granular material or the small-areaintegral projections.

In the single sheet of drawings,-

Figure 1 is a view, in vertical section, of an electric-resistancefurnace comprising the device embodying my invention;

Fig. 2 is a view, in vertical section, on the line II-II of Figure 1;

Fig. 3 is a view, in section, of a plurality of thin plates of refractomaterial surrounding a portion of the e ectrode, and

Fig. 4 is a top plan view of the group of platesillustrated in Fig. 3.

- All electric furnace 10 comprises a suitable metal framework or casing11 provided with supporting members 12.

In the casing 11 are provided outer walls 13 of heat-insulating bricksor blocks and inner walls 14 of high-temperature-resisting bricks orblocks. The inner walls 14 are suitably spaced apart to provide afurnace hamber 15 of any suitable or desired contour and dimensions.

A heating element 16, located in the chamber 15 comprises a plurality ofrefractory carbonaceous elements, built up in two parallel parts, thewhole heating element being substantially of the type described in thehereinbefore mentioned application.

A plurality of elongated electrodes 17 are provided, the inner end ofeach of the electrodes being, adapted to opera-tively engage a graphiteend block 18. A water-cooled contact terminal 19 has a wedgingengagement with the tapered outer end of the electrode 17. "Resilientcompressing means to maintain the electrode 17 in engagement with theblock 18, and the block 18 in engagement with the elements of theheating means 16, comprise a threaded rod 20, a helical spring 21, a nut22 and a washer 23 located on the threaded rod 20. A suitable anchoragefor the outer end of the resilient compressing means is provided in theshape of a bracket 24 of substantially L-shape sultably secured to themetallic casing 11 of the furnace. An insulating member 25 is placedbetween the enlarged inner end of the rod 20 and the outer surface ofthe contact terminal 19 to suitably insulate the two members from eachother.

While I have illustrated a specific embodiment of a resilientcompressing means, I desire it to be understood that this is schematiconly and any suitable construction thereof may be employed.

An insulating member 26 of asbestos may be located in the outer face ofthe wall 13, surrounding the contact terminal 19 to effectively insulateit from the casing 11.

A plurality of relatively thin refractory plates 27 are provided,substantially as illustrated in Figs. 1 and 2 of the drawing, in orderto not only operate with the resilient compression means to maintain theelectrodes in proper operative position relatively to each other and tothe other parts of the furnace but also to provide means for re- Billducing current lealrage from the two elec trodes,

It may be noted that there is not only a line contact between eachelectrode and any one of the plates immediately adjacent thereto butthat there is a possibility of the area of contact becoming larger, byreason of the wear of the electrode caused by movement of the electrodesin the wall through which they pass. It is, of course, apparent thatthere will be some movement of the electrode l7 relatively to the wall,by reason of the heating and cooling of the furnace during operation.

In order to still further increase the contact resistance existingbetween the plates 27 having fiat surface engagemen ll may separatesuccessive plates by means of a thin layer of granular material, asillustrated in Fig. 3 between the middle and the bottom plate. ll mayprovide each of the plates 27 with a plurality of integral projectionson one or both surfaces, each projection being of relatively small area.Either of these means increases the contact resistance betweensuccessive plates and this increased resistance operates tosubstantially reduce leakage; current between the electrodes or betweenany one electrode and any other part of the furnace which is at asubstantially difierent potential.

It may be noted that the use of the device embodying my inventionprovides relatively simple means for cooperating with the resilientcompressing means to mainta n the electrodes in proper operativeposition rela tively to each other and to reduce leakage current betweenthe electrodes or to other parts or the furnace.

Various modifications may be made in the device embodying my inventionwith out departing from the spirit and scope thereof and l desire thatonly such limitations shall be placed thereon as are imposed by theprior art or are specifically forth in the appended claims.

I claim as my invention:

1. An electric furnace comprising; plumesses rality of walls enclosing afurnace chamber, a resistor located in said chamber, a plurality ofspaced parallel-extending electrodes operatively engaging said resistorto conduct current thereto and therefrom, a plurality of relatively thinplates located between said electrodes and parallel thereto and meansfor spacing said plates relatively small distances apart and forpermitting only a relatively small area of contact between adjacentplate 2. An electric furnace comprising a plurality ofcurrent-conducting electrodes and means for reducing current leakagefrom said electrodes comprising a plurality of relatively thinparallel-extending refractory plates and means for permitting only arelatively small area of contact between adjacent lates.

3. An electric furnace comprising a plurality of "current-conductingelectrodes and means for supporting said electrodes in operativeposition relatively to each other and for reducing current leakage fromsaid electrodes, said means comprising a plurality of relatively thinrefractory members spaced relatively small distances apart and havingonly a relatively small area of contact between adjacent plates.

An electric furnace comprising a plurality of wflls enclosing furnacechamher, a resistor located in said chamber and supported one endthereof by one of said walls a plurality of electrodes operativelyengaging said resistor to conduct current to and from said resistor andmeans for reducing the current leakage between and from said electrodessaid means comprising a plurality of space/depart refractory memberssurrounding said electrodes intermeditheir and having only a relativelysmall area of surface contact between adjacent plates.

In testimony whereof. 'l have hereunto subscribed name this 18th day ofMay,

